Helen Thuo, who works nearby, was one of those drivers. She said she arrived downtown and didn't see barricades anywhere when she parked before dawn. She removed her vehicle about 8 a.m., after a white plastic barricade had been placed on one of the entrances.

An ALDOT crew arrived to ward off other drivers from entering the area. A water truck began filling the plastic barricades with water.

Other drivers parked as far away as the Medical Forum, BJCC and beyond, then trekked by foot beneath the interstate to their offices. Some said they began scouting other parking locations when the closure was first announced in June.

Drivers who park in the now-restricted areas face towing at their own expense, ALDOT spokeswoman Linda Crockett said.

The area underneath the bridges has long been used for parking by downtown workers and visitors attending events at nearby venues such as Boutwell Auditorium and the BJCC.

Walking through the now cleared space as traffic roared overhead, attorney Charles Salvagio said he sees the reason for the closure if ALDOT's motive is safety.

The impact of removing so many spaces will cause other problems, he said.

"I don't know how they're going to get people in here for events," Salvagio said.

The first test comes Tuesday night.

Pop singer Austin Mahone has a concert Tuesday night at the 5,000-seat Boutwell Auditorium. Five of the singer's tour buses will be allowed to park under the bridges, Crockett said.

Crockett said the allowance for the singer's tour buses to park there was made under a prior agreement.

Updated parking information for BJCC

For events at the BJCC, convention complex officials have updated their parking plan to adjust for the I-20/59 changes.

BJCC has more than 7,600 parking spaces, made up of a mix of lots owned by BJCC and public spots at the decks for Boutwell Auditorium and the former Social Security building. On-street parking also is available in the area, said Elaine Witt with the BJCC.

The complex recently finished improvements to two parking lots across Richard Arrington Jr. Boulevard, across from the Uptown Entertainment District between 23rd and 24th streets. Two parking lots between 18th and 19th streets also are being improved, Witt said.